A technique for dealing with an abnormality in the power source of the heating device is well known. In such a heating device, when voltage of abnormal waveform, such as square wave or direct current, is input, there is a possibility that a triac (power distribution adjustment member), which controls the supply of power to a heater, goes out of control. In order to deal with this problem, the heating device is provided with a circuit to detect an abnormal waveform. When the abnormal waveform is detected, the heating device cuts off the supply of power to the heater by controlling a relay.